Method and apparatus for optical imaging via spectral encoding

ABSTRACT

Method, apparatus and arrangement according an exemplary embodiment of the present invention can be provided for generating an image of at least one portion of an anatomical structure. For example, the portion can have an area greater than about 1 mm2, and the image can have a resolution a transverse resolution that is below about 10 μm. For example, light can be scanned over such portion so as to generate first information which is related to the portion, where the light may be provided through a diffraction arrangement to generate a spectrally dispersed line. Method, apparatus and arrangement according to a further exemplary embodiment of the present invention can be provided for positioning a radiation or optical beam within an anatomical structure based on signals generated by scanning a portion of the structure using the same or a different beam.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based upon and claims the benefit of priority fromU.S. Patent Application Ser. No. 60/721,802, filed Sep. 29, 2005, theentire disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to devices and methods for comprehensiveoptical imaging of epithelial organs and other biological structures viaspectral encoding.

BACKGROUND OF THE INVENTION

Radiological techniques such as X-ray computed tomography (“CT”),magnetic resonance imaging (“MRI”), and ultrasound can enablenoninvasive visualization of human pathology at the organ level.Although these modalities may be capable of identifying large-scalepathology, the diagnosis of cancer can require the evaluation ofmicroscopic structures that is beyond the resolution of conventionalimaging techniques. Consequently, biopsy and histopathologic examinationmay be required for diagnosis. Because precancerous growth and earlystage cancers often arise on a microscopic scale, they can presentsignificant challenges for identification and diagnosis. Conventionalscreening and surveillance of these pathologies relies on unguidedbiopsy and morphological analysis of Hematoxylin and Eosin (“H&E”)stained slides. Although this approach may be regarded as a currentstandard for microscopic diagnosis, it requires the removal of tissuefrom the patient and significant processing time to generate slides.More importantly, histopathology is inherently a point samplingtechnique; frequently only a very small fraction of the diseased tissuecan be excised and often less than 1% of a biopsy sample may be examinedby a pathologist.

It may be preferable to obtain microscopic diagnoses from an entireorgan or biological system in a living human patient. However, the lackof an appropriate imaging technology can greatly limits options forscreening for pre-neoplastic conditions (e.g. metaplasia) and dysplasia.In addition, an inability to identify areas of dysplasia and carcinomain situ has led to screening procedures such as, e.g., random biopsy ofthe prostate, colon, esophagus, and bladder, etc., which can be highlyundesirable and indiscriminate. Many diagnostic tasks presently referredto a frozen section laboratory, such as the delineation of surgicaltumor margins, could be improved by a diagnostic modality capable ofrapidly imaging large tissue volumes on a microscopic scale. Atechnology that could fill this gap between pathology and radiologywould be of great benefit to patient management and health care.

Technical advances have been made to increase the resolution ofnon-invasive imaging techniques such as, e.g., micro-CT, micro-PET, andmagnetic resonance imaging (“MRI”) microscopy. Resolutions approaching20 μm have been achieved by these technologies, but fundamental physicallimitations can still prevent their application in patients. Microscopicoptical biopsy techniques, performed in situ, have recently beenadvanced for non-excisional histopathologic diagnosis. Reflectanceconfocal microscopy (“RCM”) may be particularly well-suited fornon-invasive microscopy in patients, as it is capable of measuringmicroscopic structure without tissue contact and does not require theadministration of extrinsic contrast agents. RCM can reject out of focuslight and detects backscattered photons selectively originating from asingle plane within the tissue. RCM can be implemented, e.g., by rapidlyscanning a focused beam of electromagnetic radiation in a plane parallelto a tissue surface, yielding transverse or en face images of tissue.The large numerical aperture (NA) that may be used in RCM can yield avery high spatial resolution (1-2 μm), enabling visualization ofsubcellular structures. High NA imaging, however, can be particularlysensitive to aberrations that arise as light propagates throughinhomogeneous tissue. Also, high-resolution imaging with RCM istypically limited to a depth of about 100-400 μm.

RCM has been extensively demonstrated as a viable imaging technique forskin tissue. Development of endoscopic confocal microscopy systems hasbeen more difficult, owing at least in part to the substantial technicalchallenges involved in miniaturizing a scanning microscope. One majorobstacle to direct application of the concepts of confocal microscopy toendoscopy is the engineering of a mechanism for rapidly rastering afocused beam at the distal end of a small-diameter, flexible probe. Avariety of approaches have been proposed to address this problem,including the use of distal micro-electromechanical systems (“MEMS”)beam scanning devices and proximal scanning of single-mode fiberbundles. Also, RCM may provide microscopic images only at discretelocations—a “point sampling” technique. As currently implemented, pointsampling can be inherent to RCM because it has a limited field of view,which may be comparable to or less than that of an excisional biopsy,and the imaging rate can be too slow for comprehensive large fieldmicroscopy.

Another challenge in adapting confocal microscopy to endoscopicapplications can include miniaturization of high NA objectives that maybe used for optical sectioning. Such miniaturization may be achieved byproviding, e.g., a gradient-index lens system, dual-axis objectives, orcustom designs of miniature objectives. For example, detailed images ofthe morphology of cervical epithelium may be obtained in vivo using afiber optic bundle coupled to a miniature objective lens, andfluorescence-based images of colorectal lesions may be achieved usingcommercial instruments such as those which may be obtained, e.g., fromOlympus Corp. and Pentax/Optiscan.

Despite these advances, there may be a need for improved imagingtechniques that can provide microscopic resolution of biologicalstructures in situ over large regions.

OBJECTS AND SUMMARY OF THE INVENTION

One of the objects of the present invention is to overcome certaindeficiencies and shortcomings of the prior art systems and methods(including those described herein above), and provide an exemplaryembodiment of a method and an apparatus which are capable of providingcomprehensive microscopic optical imaging of anatomical structures suchas, e.g., epithelial organs or other bodily tissues.

For example, an apparatus in accordance with exemplary embodiments ofthe present invention may be in the form of a probe or an assembly,which may be disposable. The probe or assembly may include, e.g., one ormore optical waveguides capable of forwarding an electromagneticradiation to the probe or assembly and forming an optical beam, one ormore focusing arrangements provided at a distal end which may beconfigured to focus the optical beam, and a scanning arrangementconfigured to scan the beam across a portion of the anatomicalstructure. The electromagnetic radiation may include a plurality ofwavelengths, and the wavelengths may vary with time. The probe may alsoinclude one or more diffraction arrangements which may be configured todiffract or spectrally disperse the beam, one or more correctingarrangements which may be configured to correct for optical aberrations,a mechanism capable of centering or positioning the probe or assemblywithin the anatomical structure being imaged, and/or a guidewirearrangement which can be capable of translating and/or rotating theprobe or assembly. The waveguide may be, e.g., an optical fiber or abundle of optical fibers or other waveguides. The probe or assembly mayfurther include a spectral encoding arrangement and/or a correctiveoptical arrangement such as, e.g., a curved transparent surface, whichcan be used to correct aberrations such as an astigmatism in the opticalbeam path.

In certain exemplary embodiments of the present invention, the probe orassembly can be configured to scan a region of the anatomical structurewhich can have an area greater than about 1 mm², and where the regionmay include a surface, a volume, or a location below a surface of theanatomical structure. The probe or assembly may be configured to obtaindata which can be used to generate an image of the region with aresolution that is below approximately 10 μm.

In further exemplary embodiments of the present invention, a probe orassembly can be provided which is capable of positioning and/or focusthe optical beam relative to the anatomical structure. The positioningand/or focusing can be based on, e.g., an interferometric signal, atime-of-flight signal, or an intensity of the electromagnetic radiation.The probe or assembly can include a confocal optical arrangement thatcan

In still further exemplary embodiments of the present invention, theprobe or assembly can include a locating arrangement that is capable ofdetermining a location of the probe or assembly relative to a locationwithin the anatomical structure, and an optional positioning arrangementthat can control the motion and/or position of the probe based on thelocation.

In other exemplary embodiments of the present invention, a method forobtaining comprehensive microscopic optical imaging of anatomicalstructures can be provided, which can include scanning a region of theanatomical structure to be imaged that is larger than about 1 mm² usingan electromagnetic radiation such as, e.g., an optical beam, receiving asignal based on the radiation, and generating an image based on thesignal, where the image can have a transverse resolution that is belowabout 10 μm.

In yet further exemplary embodiments of the present invention, a methodfor positioning or directing an electromagnetic radiation within ananatomical structure is provided, which can include scanning at least aportion of the anatomical structure using the electromagnetic beam, andusing a signal which may be based on the electromagnetic radiation tocontrol the position and/or focus of the radiation. A method can also beprovided to control the position or focus of a confocal beam within theanatomical structure based on a signal obtained from scanning theelectromagnetic radiation over a region of the anatomical structure.

Other features and advantages of the present invention will becomeapparent upon reading the following detailed description of embodimentsof the invention, when taken in conjunction with the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features and advantages of the present invention willbecome apparent from the following detailed description taken inconjunction with the accompanying figures showing illustrativeembodiments of the present invention, in which:

FIG. 1 is a schematic illustration of an exemplary spectrally encodedconfocal microscopy (SECM) system;

FIG. 2A is an exemplary SECM image of a swine intestinal epithelium,obtained ex vivo, 100 μm from the tissue surface using a single modesource and single-mode detection (SM-MM) configuration;

FIG. 2B is another exemplary SECM image of a swine intestinalepithelium, obtained using a single-mode source and multi-mode detection(SM-MM) configuration;

FIG. 2C is a magnified view of an SECM image of a swine intestinalepithelium;

FIG. 3A is an exemplary SECM image of a swine intestinal epithelium,obtained ex vivo, after compression of the bowel wall at an imagingdepth of 50 μm;

FIG. 3B is an exemplary SECM image of a swine intestinal epithelium,obtained ex vivo, after compression of the bowel wall at an imagingdepth of 100 μm;

FIG. 4 is a schematic illustration of an exemplary SECM apparatus;

FIG. 5 is an exemplary SECM image of a USAF chart;

FIG. 6A is an exemplary SECM image based on data taken from a lens papersample, displayed at a magnification of 1×;

FIG. 6B is an exemplary SECM image based on data taken from a lens papersample, displayed at a magnification of 4.5×;

FIG. 6C is an exemplary SECM image based on data taken from a lens papersample, displayed at a magnification of 16.7×;

FIG. 6D is an exemplary SECM image based on data taken from a lens papersample, displayed at a magnification of 50×;

FIG. 6E is an exemplary SECM image based on data taken from a lens papersample, displayed at a magnification of 125×;

FIG. 7 is a series of exemplary SECM data obtained from a lens papersample at five different focal positions, together with a combine imagethat was generated by combining the data in the five individual images;

FIG. 8A is an exemplary SECM image based on data taken from a swineintestinal tissue fragment, displayed at a magnification of 1×;

FIG. 8B is an exemplary SECM image based on data taken from a swineintestinal tissue fragment, displayed at a magnification of 4×;

FIG. 8C is an exemplary SECM image based on data taken from a swineintestinal tissue fragment, displayed at a magnification of 20×;

FIG. 8D is an exemplary SECM image based on data taken from a swineintestinal tissue fragment, displayed at a magnification of 40×;

FIG. 9 is a schematic illustration of an exemplary SECM system capableof imaging large tissue volumes;

FIG. 10 is a schematic illustration of a distal end of an exemplarycatheter that may be used for imaging in accordance with exemplaryembodiments of the present invention;

FIG. 11 is a schematic illustration of an exemplary catheter that may beused for imaging in accordance with exemplary embodiments of the presentinvention that includes an external rotational scanning arrangement;

FIG. 12 A is a schematic illustration of optical effects of a curvedwindow and a negative cylindrical lens;

FIG. 12B is a schematic illustration of an astigmatic aberrationcorrection using a curved window;

FIG. 13A is an illustration of an exemplary technique which may be usedto acquire the desired depth range by stepping through a range of focaldepths;

FIG. 13B is an illustration of an exemplary technique which may be usedfor imaging tissue at a particular depth by actively adjusting a focalplane;

FIG. 14A is a schematic illustration of a dual bimorph piezoelectricbender;

FIG. 14B is a schematic illustration of an exemplary arrangement wherebya motor may be moved within a transparent outer sheath using bendingactuators;

FIG. 15 is a schematic illustration of an exemplary balloon catheterdesign that is configured to control a focus by translating acollimating lens;

FIG. 16 is a photograph of a particular variable-focus lens;

FIG. 17A is a schematic illustration of a cylindrical inner housingdesign which has a form of a transparent cylinder;

FIG. 17B is a schematic illustration of a cylindrical inner housingdesign which includes a transparent window;

FIG. 17C is a schematic illustration of a cylindrical inner housingdesign which includes several openings in the housing wall;

FIG. 17D is a schematic illustration of a cylindrical inner housingdesign which includes openings in a connection between the housing and amotor;

FIG. 18 is a schematic illustration of electrical and data connectionsbetween components of an exemplary imaging system;

FIG. 19A is an illustration of an exemplary probe scanning pattern inwhich a beam is rotated quickly and simultaneously displaced slowly inan axial direction to provide a spiral imaging pattern;

FIG. 19B is an illustration of an exemplary probe scanning pattern inwhich the beam is rotated quickly and then repositioned axially;

FIG. 19C is an illustration of an exemplary probe scanning pattern inwhich the beam is rapidly scanned in the axial direction and thenrepositioned in the rotational direction;

FIG. 19D is an illustration of an exemplary probe scanning pattern inwhich the beam is scanned over concentric circular paths cover acircular tissue area;

FIG. 20A is a schematic illustration of a rapid exchange ballooncatheter design which includes a guidewire arrangement located at adistal tip of a housing;

FIG. 20B is a schematic illustration of a rapid exchange ballooncatheter design which includes the guidewire arrangement located at thedistal tip of the housing and having a form of a secondary channel;

FIG. 20C is a schematic illustration of a rapid exchange ballooncatheter design which includes the guidewire arrangement located at aproximal tip of a housing and having a form of a secondary channel;

FIG. 21A is a schematic illustration of a first step in an exemplarytechnique for positioning a wire balloon catheter that includesinsertion of a guidewire;

FIG. 21B is a schematic illustration of a second step in an exemplarytechnique for positioning a wire balloon catheter that includes placinga balloon catheter over the guidewire;

FIG. 21C is a schematic illustration of a third step in an exemplarytechnique for positioning a wire balloon catheter that includes placingan optical arrangement in the balloon catheter;

FIG. 22A is a schematic illustration of an exemplary balloon catheterwhich includes a single channel configured to deliver an inflationmaterial from a remote location to the balloon;

FIG. 22B is a schematic illustration of an exemplary balloon catheterwhich includes two sheaths, where the inflation material can be providedbetween the sheaths;

FIG. 23A is a schematic illustration of a centering arrangement having aform of a wire cage, where the arrangement is contained within an outersheath;

FIG. 23B is a schematic illustration of the centering arrangement havingthe form of a wire cage, where the arrangement is partially protrudingfrom the outer sheath;

FIG. 23C is a schematic illustration of the centering arrangement havingthe form of a wire cage, where the arrangement is fully extended fromouter sheath;

FIG. 24A is a schematic illustration of an exemplary SECM/SD-OCT systemwhich includes a wavelength division multiplexer and a dispersioncompensator;

FIG. 24B is a schematic illustration of an exemplary spectrum which maybe provided by an SECM/SD-OCT system using a linear CCD array;

FIG. 25 is a schematic illustration of an exemplary SECM/SD-OCT probe;

FIG. 26 is a schematic illustration of an exemplary SECM/SD-OCT probewhich includes a single optical fiber for both the SECM and the SD-OCTarrangements;

FIG. 27 is an exemplary flow diagram of a technique which may be used toadjust a focus for an SECM image using SD-OCT data;

FIG. 28 is a schematic illustration of a cross section of an exemplarycatheter cable;

FIG. 29 is a schematic illustration of an exemplary probe which includesa beam deflection optical arrangement that may provide a more compactprobe configuration;

FIG. 30A is a schematic illustration of a translational scanningtechnique showing a compact configuration of a probe during delivery ofthe probe to the site to be imaged;

FIG. 30B is a schematic illustration of the translational scanningtechnique showing an inner housing of the probe positioned at a distallimit of a translational range;

FIG. 30C is a schematic illustration of the translational scanningtechnique showing the inner housing of the probe positioned at aproximal limit of the translational range;

FIG. 31 is a schematic illustration of an outer housing which includestransparent openings;

FIG. 32 is a schematic illustration of an exemplary compact probe whichincludes an off-center collimation optical arrangement and which isconfigured to provide external rotational scanning;

FIG. 33A is a schematic illustration of a probe which includes a forwardinflatable balloon and an inner housing that is configured to scan whilein contact with an inner wall of the balloon;

FIG. 33B is a schematic illustration of the probe shown in FIG. 33Awhich is in contact with an inner wall of the inflated balloon;

FIG. 34A is a schematic illustration of an exemplary probe that includesan outer inflatable balloon and an inner inflatable balloon which may beconfigured to maintain contact between the probe and a wall of the outerballoon when inflated;

FIG. 34B is a schematic illustration of the probe shown in FIG. 34A,where the inflated inner balloon is provided around the probe and isconfigured to maintain contact between the probe and the wall of theinflated outer balloon;

FIG. 35A is a schematic illustration of a further exemplary probe thatincludes an outer inflatable balloon and an inner inflatable balloonwhich may be configured to maintain contact between the probe and a wallof the outer balloon when inflated;

FIG. 35B is a schematic illustration of the probe shown in FIG. 35A,where the inflated inner balloon is provided between the probe and theouter balloon and is configured to maintain contact between the probeand the wall of the inflated outer balloon;

FIG. 36A is a schematic illustration of a bottom view of a probe that isconfigured to scan along a pullback axis while in contact with an innerwall of an inflatable balloon;

FIG. 36B is a schematic illustration of a side view of the probe shownin FIG. 36A;

FIG. 36C is a schematic illustration of a side view of the probe shownin FIG. 36A, where the probe is in contact with the inner wall of theinflated balloon; and

FIG. 36D is a front view of the probe shown in FIG. 36C.

Throughout the figures, the same reference numerals and characters,unless otherwise stated, are used to denote like features, elements,components or portions of the illustrated embodiments. Moreover, whilethe subject invention will now be described in detail with reference tothe figures, it is done so in connection with the illustrativeembodiments. It is intended that changes and modifications can be madeto the described embodiments without departing from the true scope andspirit of the subject invention as defined by the appended claims.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF INVENTION

In accordance with exemplary embodiments of the present invention, amethod and apparatus for endoscopic confocal microscopy is providedwhich circumvents the need for miniature, high-speed scanning mechanismswithin a probe. Spectrally encoded confocal microscopy (“SECM”) is awavelength-division multiplexed confocal approach that may be used. SECMutilizes a broad bandwidth light source and can encode one dimension ofspatial information in the optical spectrum.

An exemplary SECM technique is shown in FIG. 1. The output from asingle-mode optical fiber 100, which may be located at a distal end of aprobe, can be collimated by a collimating lens 110, and then illuminatea dispersive optical element (such as, e.g., a transmission diffractiongrating 120). An objective lens 130 can then focus each diffractedwavelength to a distinct spatial location within the specimen, resultingin a transverse line focus 140 where each point on the line may becharacterized by a distinct wavelength. After reflection from thespecimen, which may be, e.g., biological tissue, the optical signal canbe recombined by the diffraction element 120 and collected by thesingle-mode fiber 100. The core aperture of the single-mode fiber 100can provide a spatial filtering mechanism that is capable of rejectingout-of-focus light. Outside the probe (and optionally within a systemconsole) the spectrum of the returned light can be measured andconverted into confocal reflectance as a function of transversedisplacement within the specimen. The spectral decoding can be performedrapidly. Thus an image created by scanning the beam in a directionorthogonal to the line focus can be accomplished by relatively slow andstraightforward mechanical actuation.

SECM techniques may allow the use of endoscopic RCM, and it can becapable of providing image data at extremely high rates using high-speedlinear CCD cameras. Commercially available linear CCD arrays can obtaindata at a rate greater than about 60 million pixels per second. Whenincorporated into an SECM spectrometer, these arrays can produceconfocal images at speeds that are about 10 times faster than a typicalvideo rate and up to 100 times faster than some endoscopic RCMtechniques. The rapid imaging rate and fiber-optic design of typicalSECM systems can permit comprehensive, large area microscopy through anendoscopic probe.

Techniques using optical coherence tomography (“OCT”) and variationsthereof may be used for comprehensive architectural screening. Acquiringan OCT signal in the wavelength domain, rather than in the time domain,can provide orders of magnitude improvement in imaging speed whilemaintaining excellent image quality. Using spectral domain OCT(“SD-OCT”) techniques, high-resolution ranging can be conducted inbiological tissue by detecting spectrally resolved interference betweena tissue sample and a reference. Because SD-OCT systems can utilize thesame high-speed linear CCD's as SECM systems, they can also be capableof capturing images at 60 million pixels/s, which is approximately twoorders of magnitude faster than conventional time-domain OCT (“TD-OCT”)systems. With this acquisition rate and resolution, SD-OCT systems canprovide comprehensive volumetric microscopy at the architectural levelin a clinical environment.

The information provided by exemplary SD-OCT and SECM systems can becomplementary, and a hybrid platform utilizing both techniques canprovide information on the architectural and cellular structure oftissue that may be essential to accurate diagnosis. Although acombination of disparate technologies typically requires extensiveengineering and may compromises performance, SECM and SD-OCT systems canshare key components, and a high-performance multi-modality system canbe provided without substantially increasing complexity or cost of theindividual systems.

An SECM system in accordance with certain exemplary embodiments of thepresent invention can utilize a wavelength-swept 1300 nm source and asingle-element photodetector to obtain spectrally encoded information asa function of time. With this system, images can be acquired at rates ofup to about 30 frames/second having high lateral (1.4 μm) and axial (6μm) resolutions, over a 400 μm field of view (“FOV”). Images of freshlyexcised swine duodenum segments were imaged ex vivo with a high speedsystem to illustrate the capability of an SECM system to identifysubcellular structures that may be found in, e.g., specializedintestinal metaplasia (“SIM”) or the metaplastic change of Barrettsesophagus.

FIGS. 2A-2C depict exemplary SECM images of a swine intestinalepithelium obtained ex vivo using two imaging modes and correspondingfiber configurations: a single-mode illumination with single-modedetection (“SM-SM”), and a single-mode illumination with multi-modedetection (“SM-MM”). The SM-SM image in FIG. 2A shows the epitheliumstructure located 100 μm from the tissue surface using a single modesource and single-mode detection. The image of the same tissue regionshown in FIG. 2B, obtained using a using a single mode source andmulti-mode detection (SM-MM) with a core:aperture ratio of 1:4, may havea smoother appearance and may be more easily interpreted because of areduction in speckle noise. FIG. 2C is a magnified view of the imageshown in FIG. 2B that indicates a presence of villi containing a poorlyreflecting core (e.g., lamina propria or “lp”) and a more highlyscattering columnar epithelium. Bright image densities visible at thebase of the columnar cells, consistent with nuclei (indicated by arrows)are shown in FIG. 2C.

The thickness of an esophageal wall being imaged in vivo using OCTtechniques can be decreased, e.g., by about a factor of two using aninflated balloon. The swine intestinal sample thickness shown in FIGS.2A-2C was decreased by the same amount, and the subcellular featuresobserved using SECM techniques were well preserved. FIGS. 3A and 3B showimages of this thinned sample obtained at a depth of 50 μm and 100 μm,respectively.

The penetration depth of a commercial 800 nm laser scanning confocalmicroscope was observed to be reduced by about 20% as compared to thatobtained with a 1300 nm SECM system. This reduced penetration may be aresult of increased scattering of the shorter wavelength source. Thus anSECM system using an 840 nm source may provide sufficient penetration toidentify subcellular structure of, e.g., an intestinal epithelium.

An apparatus in accordance with certain exemplary embodiments of thepresent invention that is configured to provide comprehensive SECMimages is illustrated schematically in FIG. 4. This exemplary apparatuscan be configured to obtain images from a cylindrical sample having alength of 2.5 cm and a diameter of 2.0 cm, which are approximately thedimensions of the distal esophagus. A fiber-coupled 2.0 mWsuperluminescent diode 200, having a wavelength centered at 800 nm and abandwidth of 45 nm (QSSL-790-2, qPhotonics, Chesapeake, Va.) can beconfigured to illuminate a 50/50 single-mode fiber optic beam splitter405. Light transmitted through one port of the splitter can becollimated by a collimator 410 and transmitted through a fiber 412 to afocusing apparatus 415 and to a grating-lens pair that includes agrating 420 (1780 lpmm, Holographix, LLC, Hudson, Mass.) and a 350230-Basphere lens 425 (Thor Labs, Inc., Newton, N.J.) having a focal length,f, of 4.5 mm, a clear aperture of 5.0 mm, and a NA of 0.55. Thisarrangement can be capable of producing a 500 μm longitudinal lineararray, or line, of focused, spectrally-encoded spots 430 on an interiorsurface of the cylindrical sample. The grating-lens pair may be affixedto a shaft of a motor 435 (e.g., a 1516SR, 15 mm diameter motor obtainedfrom MicroMo Electronics, Inc., Clearwater, Fla.) by a housing 440. Asthe motor 435 rotates, the spectrally encoded line can be scanned acrossthe inner circumference of the cylindrical sample. The motor 435,housing 440, and grating-lens pair may be translated along alongitudinal axis of the cylindrical sample during rotation of the motor435 using, e.g., a computer-controlled linear stage 445 (such as, e.g.,a Nanomotion II, 2.5 cm range, obtained from Melles Griot, Rochester,N.Y.). This procedure produced a helical scan of the entire interiorsurface of the cylindrical sample.

Light reflected from the sample can be transmitted back through theoptical system into the single-mode fiber 412 and provided by the fiber412 to a spectrometer 450 and linear CCD 455 that can include, e.g.,2048 pixels and has a 30 kHz line rate (such as, e.g., a Basler L104K,obtained from Basler Vision Technologies, Exton, Pa.). A computer 460can be used to store, analyze and display image data provided by thespectrometer 450 and CCD 455. Approximately 60,000 points per motorrotation (at 0.5 Hz, or 30 rpm) may be digitized. to provide acircumferential sampling density of approximately 1.0 μm. Thelongitudinal velocity of the motor can be approximately 0.25 mm/s andthe time required for one complete scan of the cylindrical sample may beabout 100 seconds.

The 1/e² diameter of the collimated beam on the grating-lens pair can beabout 4.0 mm. As a result, the effective NA of this exemplary apparatuscan be approximately 0.4, which corresponds to a theoretical spotdiameter of approximately 1.2 μm and a confocal parameter ofapproximately 2.5 μm. In a system that is free of optical aberrations, atheoretical spectral resolution on the sample may be 0.8 Å, which canyield up to approximately 630 resolvable points across the spectrallyencoded line 430. The spectrometer 450 in the detection arm can bedesigned to exceed the predicted spectral resolution of the probe.

An SECM scan of a 1951 USAF resolution chart obtained using thisapparatus is shown in FIG. 5. The smallest bars in this Figure, whichare separated by 2.2 μm, were resolved. A transverse line spreadfunction full-width-half-maximum (“FWHM”) and an axial FWHM functionobtained using a mirror scanned through the focus were measured as 2.1μm and 5.5 μm, respectively. The field of view was observed to be about500 μm. These measurements were slightly lower than correspondingtheoretical values, which may be attributed to aberrations in theoptical path. These parameters indicate that the exemplary apparatusdescribed herein can be capable of providing sufficient resolution to beused for confocal microscopy in biological tissue.

Exemplary SECM image data for a complete pullback image of a 2.5 cmphantom specimen are shown in FIG. 6. Polar coordinates were convertedto rectangular coordinates prior to generating these displayed images.The phantom specimen was made using lens paper affixed to the innersurface of a 2.1 cm inner diameter Teflon tube. In a low magnificationimage shown in FIG. 6A, macroscopic structure of the paper, includingfolds and voids, can be observed. Circumferential stripes that arevisible may have resulted from the lower spectral power and lensaberrations that may be present at or near the ends of thespectrally-encoded line. Individual fibers and fiber microstructure canbe clearly resolved in regions of this data set that are presented athigher magnifications, as shown in FIGS. 6B-6E.

By adjusting the focusing apparatus 415 in FIG. 4A, cylindricaltwo-dimensional (“2D”) images of the phantom sample were acquired atfive discrete focal depths over a range of 120 μm. These five images710-750 shown in FIG. 7 were then summed to create an integrated image760, which demonstrates a nearly complete coverage of the surface of thephantom sample.

Imaging biological samples using an SECM apparatus such as thatdescribed herein can be complicated by the lack of a centering apparatusfor the optical scan head. In order to provide further improvements forgenerating wide-field microscopy images and data, a sample of swineintestine was placed on top of a 2.0 cm diameter transparent cylinder. A360° scan of this sample, which was acquired in 1 second, is shown inFIG. 8A. Imaged tissue likely appears in only one sector of thecylindrical scan because the probe was not centered and the sample didnot wrap completely around the cylinder. FIGS. 8B-8D show a sequence ofexemplary magnified regions of this tissue sample. The image shown inFIG. 8B is an expansion of a 1.5 cm sector outlined by a dottedrectangle in FIG. 8A. Similarly, the image in FIG. 8C represents anexpansion of the rectangle outlined in FIG. 8B, and the image in FIG. 8Drepresents an expansion of the rectangle outlined in FIG. 8C. Magnifiedimages of the tissue in the image FIG. 8B are suggestive of a glandularstructure. The magnified images in FIGS. 8C-8D exhibit villi and nuclearfeatures that are similar to those observed using a 1300 nm SECM system,as shown in FIGS. 2 and 3. Other areas of the SECM scan in FIG. 8A showartifacts, including specular reflectance from the transparent cylinderand complete signal dropout, both of which may result from improperpositioning of a focused SECM beam.

Conducting comprehensive confocal microscopy in patients can present avariety of technical challenges. Such challenges may include, e.g.,increasing the imaging rate, miniaturizing the probe optical componentsand mechanical components, incorporating a centering mechanism, andimplementing a technique for dynamically changing the focal plane.

The image acquisition speed of an SECM system can be improved by, e.g.,a factor of about 2-4 as compared with the exemplary system describedhereinabove. Such an improvement can be realized by providing certainmodifications. For example, a higher power semiconductor light source(such as, e.g., a Superlum Diode, T-840 HP: 25 mW, 840 nm, 100 nmspectral bandwidth) can provide, e.g., approximately 1000 spectrallyresolvable points. Such an increase in optical power can improvesensitivity and a larger bandwidth may widen the field of view, makingit possible to scan the SECM beam approximately two times faster. Also,using an optical circulator such as, e.g., an OC-3-850 (Optics forResearch, Caldwell, N.J.) can increase the efficiency of light deliveredto the probe and collected from the probe. Using a faster, moresensitive linear CCD such as, for example, an AVIIVA M4-2048 having 2048pixels and a 60 kHz readout rate (Atmel Corporation) can provide atwofold increase in data acquisition speed and an improved spectralresponse over the wavelength range used to generate image data.Performance may also be improved by using, e.g., a Camera Link interfacethat can be capable of transferring data at a rate of approximately 120MB/s from a camera to a hard-drive array for storage.

Sensitivity, which can be understood to refer to a minimum detectablereflectance, is a system parameter that can affect confocal imagequality and penetration depth. A fraction of the incident light, whichmay be approximately 10⁻⁴ to 10⁻⁷, can be reflected from skin at depthsup to approximately 300 μm when using a near-infrared RCM technique.Based on the NA of the objective lens used in the exemplary system inaccordance with certain exemplary embodiments of the present inventiondescribed herein, and the observation that skin may attenuate light moresignificantly than non-keratinized epithelial mucosa, the exemplary SECMprobe objective described herein may collect approximately 3×10⁻⁴ to3×10⁻⁷ of the illuminating light reflected from deep within tissue. A 25mW light source may be separated into, e.g., approximately 1000independent beams. A maximum double pass insertion loss can be estimatedto be approximately 10 dB (which can include a 6 dB loss from the probe,and a 4 dB loss from the fiber optics and spectrometer). Each pixel inan array may thus be illuminated by approximately 50 to 50,000photons/pixel for each line integration period based on these estimatedparameters.

Using a multi-mode detection technique, a factor of 10 signal gain maybe achieved, resulting in approximately 500 to 500,000 photons/pixel perscan for such a configuration. A single pixel on an Atmel AVIIVA M4camera, e.g., can reliably detect light if a signal is above the darkcurrent fluctuation that occurs at approximately 240 photons. If thisdevice has approximately a 50% quantum efficiency at these wavelengths,a minimum detectable signal can be produced at approximately 480photons/pixel per scan. Based on these approximations, an Atmel cameramay have sufficient sensitivity to allow SECM imaging at deeper tissuedepths. Quantum noise-limited detection of a predicted minimumreflectance can be achieved by using a multi-mode fiber for collectionor by increasing the source power.

A schematic diagram of an apparatus capable of performing large-areamicroscopic imaging of epithelial organs in accordance with certainexemplary embodiments of the present invention is shown in FIG. 9. Alight source 900, which may be a broadband source or a wavelength sweptsource, can provide light which may be conveyed through a circulator 910or, alternatively, through a fiber splitter. The light can then betransmitted to an imaging catheter 930 through a scanning mechanism 920.Scanning can be performed either externally to the catheter or withinthe catheter. In certain preferred exemplary embodiments, pullbackscanning may be performed outside the catheter, and rotational scanningmay be performed inside the catheter. Reflected light that is collectedmay then be detected with a detector 940 which may be, e.g., aspectrometer if a broadband light is used. The detector 940 may also be,e.g., a single detector if a wavelength swept source is used. Dataprovided by the detector 940 may be processed, displayed and/or saved bya computer 950 which may also be configured to control and synchronizethe scanning procedure.

Screening large luminal organs may preferably utilize a centering of adistal portion of a catheter within the lumen to provide a consistentfocus distance and/or depth relative to the tissue, and rapidacquisition of circumferential images over lengths of severalcentimeters. These criteria can be satisfied by incorporating acircumferentially scanning imaging probe within a centering device.Provided an imaging optical arrangement located at or near the middle ofthe centering device can provide several additional advantages,including, e.g., elimination of surface height fluctuations, which maysimplify focusing requirements, and physical coupling of the imagingsystem to a patient, which can greatly reduce motion artifacts that mayotherwise occur.

A schematic diagram of the distal end of an SECM catheter in accordancewith certain exemplary embodiments of the present invention is shown inFIG. 10. Light can be provided through an optical fiber 1000, which maybe fixed by a fiber chuck 1005, and then collimated using a collimatinglens 1010. This light may then pass through a variable focusingmechanism 1015 and a cylindrical lens 1020 that can be configured topre-compensate the optical path to correct for astigmatism effects. Thelight may then be diffracted through a diffraction grating 1025, whichcan be configured to diffract a center wavelength of the light by, forexample, approximately 90 degrees, and focused by an imaging lens 1030onto a spectral encoded line 1035.

Speckle artifact may be reduced using multi-mode detection by increasingthe diameter of a pinhole aperture associated with the optical fiber1000. This technique can provide an increased signal throughput and areduction in speckle artifacts, together with only a slight decrease inspatial resolution. A double clad optical fiber may be used to implementthis technique for spectral encoding, in which a single-mode core canilluminate a tissue and a multi-mode inner cladding can detect reflectedlight.

The imaging lens 1030 may preferably have a relatively large workingdistance that can be, e.g., approximately 2-7 mm, and maintain a largeNA of approximately 0.25 to 0.5. In addition, the imaging lens 1030 canbe thin, preferably not more than about 5 mm thick. Conventional lenses,such as aspheres or achromats, may be used as imaging lenses.

The inner housing 1040 may surround some or all of the various opticalcomponents and the motor 1045, and it may allow for longitudinalpositioning of these components within the outer housing 1060. The innerhousing 1040 can include portions thereof that have good opticaltransmission characteristics and low wavefront distortion to allow highquality imaging, while still maintaining structural rigidity to maintaina motor shaft 1050 centered within the probe. Materials that may be usedto form transparent windows as part or all of the inner housing 1040 mayinclude, for example, glass or plastic materials such as, e.g., Pebaxand high-density polyethylene (HDPE).

The outer housing 1060 can surround the inner housing 1040, and can beconfigured to remain in a fixed position relative to the imaged tissue1080 using the centering mechanism 1065. An opening in a wall of theouter housing 1060 can allow a pullback cable 1065 to move the innerhousing 1040. Linear scanning can be conducted by affixing the innerhousing 1040 to a computer-controlled translator (such as a translatorthat may be provided, e.g., by Newport Corp., Irvine, Calif.), whilemaintaining the outer housing 1060 in a fixed position relative to thetissue 1080 being imaged. Such a pullback technique may be used, e.g.,to obtain longitudinal esophageal OCT images. All or a portion of theouter housing 1060 may be transparent to allow a transmission of lighttherethrough. Optical characteristics of the transparent portions of theouter housing 1060 can be similar to those of the inner optical window1055.

The cylindrical lens 1020, the diffraction grating 1025, and the imaginglens 1030 may be housed in a rotational housing 1070, which may beattached to the motor shaft 1050. A conventional motor 1045 may be used,which can have a diameter as small as about 1.5 mm or less. Using anencoder may improve image quality and registration, and may alsoincrease the diameter of the motor 1045 to approximately 6-10 mm. Such amotor can be provided, e.g., by (MicroMo Electronics, Inc. (Clearwater,Fla.). Dimensions of motor wires can be minimized to limit obstructionof a field of view of the apparatus. Circumferential scanning may beperformed by rotating the rotational housing 1070 within the innerhousing 1040 using the motor 1045 via the motor shaft 1050.

A catheter configured to provide rotation of the inner housing 1040relative to the external housing 1060 from a location external to adistal end of the catheter, in accordance with certain exemplaryembodiments of the present invention, is illustrated schematically inFIG. 11. A rotary motion can be transmitted through an optical rotaryjunction 1100, and light may be coupled into a rotation optical fiber1110. The rotary junction may also maintain electrical contact via oneor more electrical wires 1120 and mechanical contacts via a rotatablepullback cable 1030 that can be configured to control pullback andfocusing mechanisms. In the exemplary apparatus configuration shown inFIG. 11, the inner housing 1140 does not surround a motor and thus itcan be smaller and lighter.

A cylindrical lens may be used to correct for astigmatism effects thatcan be created by a wall of a balloon or another centering device and/orby a transparent window or a transparent section of the inner and/orouter housing. A curved glass can induce astigmatism in a manner similarto that of a negative cylindrical lens. For example, the astigmatisminduced by the two curved transparent walls shown in FIG. 12A areoptically similar to the negative cylindrical lens shown towards theright side of this Figure. Light passing through the central dashed lineof any of the objects shown in FIG. 12A may have a shorter path thanlight passing through the upper or lower dashed lines, which leads toinduced astigmatism. Efficient and accurate correction of this opticaldistortion can be achieved, e.g., by placing a curved window, similar tothe window that induces the astigmatism, in the optical path, as shownin FIG. 12B. The curvature axis of the correcting curved window shouldbe perpendicular to the axis of the curved housing windows to provideoptical correction of the astigmatism.

In another exemplary embodiment of the present invention, an endoscopicSECM system can be provided that is capable of comprehensively imagingan organ without user intervention during the acquisition of image data.The system can be capable of accounting for motion due to, e.g.,heartbeat, respiration, and/or peristalsis movements. Utilization of acentering mechanism can greatly reduces artifacts caused by motion ofthe tissue being imaged. For example, variations in distance between animaging arrangement and the tissue being imaged can vary, for example,by as much as approximately ±250 μm during one comprehensive scan. Thisdistance variation can occur on a slow time scale (e.g., over severalseconds) relative to a circumferential scanning speed, but it may besignificant relative to a time required to scan the length of a tissueregion being imaged during longitudinal pullback of the imagingarrangement.

An exemplary technique can be used in accordance with certain exemplaryembodiments of the present invention to reduce or eliminate the effectsof tissue motion during sampling. This technique, illustrated in FIG.13A, can include a procedure for obtaining image data over a wider rangeof focal depths. If a desired total imaging depth is, for example, 200μm, and a variation in tissue distance from the imaging arrangement is,e.g., ±250 μm, then image data can be acquired over a focal range ofabout 700 μm. This procedure can ensure that image data is obtainedthroughout the desired tissue volume. Although many portions of thevolumetric image may not contain tissue when imaged, it is likely thatat least one good image would be obtained from most regions of thetissue volume of interest.

A second exemplary technique that may be used to compensate for motionof tissue during imaging is illustrated in FIG. 13B. This technique caninclude a procedure for determining a distance between the imaging lensand a surface of the tissue being imaged. This distance can be tracked,and a focus of the lens can be adaptively controlled to provide a knownfocal distance relative to the tissue surface throughout the acquisitionof image data in the tissue volume of interest. Adaptive focusing candecrease the number of focal scans required, and therefore may alsodecrease the time needed to obtain comprehensive coverage of the tissuevolume of interest. Focus of the beam can be controlled, e.g., using aninterferometric signal, a time-of-flight signal, an intensity of theelectromagnetic radiation, etc.

The above-described exemplary techniques for addressing motion of thetissue being imaged can utilize a mechanism for adjusting the focaldistance of the imaging arrangement. There are several exemplarytechniques that may be used for adjusting the focal depth within thetissue volume being imaged. For example, an inner housing of the imagingarrangement that includes a focus lens can be moved relative to anexterior housing. To achieve this motion, for example, multi-layeredbimorph piezoelectric actuators 1410 (e.g., D220-A4-103YB, PiezoSystems, Inc., Cambridge, Mass.) shown in FIG. 14A can be attached to,e.g., a metal sheet 1420 at both ends, which may provide a buckling ofthe ceramic material. These actuators can be placed back-to-back, asshown in FIG. 14A, which can effectively double the range of their freemotion. Four such actuators 1430 can be arranged between an outer sheath1440 and an assembly 1450 that can include a motor and focal opticalcomponents surround the motor, as shown in FIG. 14B. These actuators1430 can be utilized to change the focal position over the requiredrange by controllably displacing the assembly 1450 relative to the outerhousing 1440. This technique can require the presence of a high voltagewithin the probe, additional electrical wires that may traverse andinterrupt the field of view, and/or an increase of the overall diameterof a probe containing the imaging arrangement by, e.g., several mm.

An alternate exemplary technique that may be used to adjust the focaldistance of the imaging arrangement is shown in FIG. 15. A cable housing1510 can be provided that surrounds a cable 1530. The cable 1530 can beattached at one end to a collimating lens 1540, which may be configuredto be movable in a longitudinal direction relative to a housing 1550.The collimating lens 1540 can be moved relative to the housing 1550 andother optical components to vary the focal distance. This translationcan be controlled, e.g., externally to the imaging catheter, using thecable 1530 as is illustrated in FIG. 15. Alternatively, motion of thecollimating lens 1540 can be controlled, e.g., by an electric orpiezoelectric motor that can be provided inside the catheter. The focaldistance can also be varied by moving an optical fiber 1520, which canprovide the light used to image tissue, relative to the collimating lens1540. Alternatively, both the optical fiber 1520 and the collimatinglens 1540 may be moved relative to each other to vary the focaldistance.

The focal length can be shifted by a distance Δz by changing theseparation between the optical fiber 1520 and the collimating lens 1540by a distance of approximately M²Δz, where M is a magnification factorof the imaging apparatus. For example, an exemplary imaging apparatuscan have a magnification factor that is approximately 3. To obtain achange in the focal distance of approximately ±450 μm, the distancebetween the optical fiber 1520 and the collimating lens 1540 would needto move approximately ±4.0 mm, which is a distance that can be achievedusing any of the techniques described above for changing the focaldistance.

A further exemplary technique that can be used to vary the focaldistance can be to utilize an electronically tunable variable lens. Forexample, a commercially available lens 1600 (Varioptic AMS-1000, Lyon,France) shown in FIG. 16, which may be used in cell phone cameras, maybe utilized to vary the focal length in an imaging apparatus inaccordance with an exemplary embodiment of the present invention. Thislens 1600 uses an electrowetting principle, and can provide a variablefocal length between about −200 mm and 40 mm, with optical quality thatmay only be limited by diffraction effects. The current effective clearaperture (CA) of this exemplary lens 1600 is 3.0 mm and the total outerdiameter (OD) is 10 mm. A similar lens having a 4.0 mm CA and a 6.0 mmOD may be possible to produce. The full-range response time of thisexemplary lens 1600 is about 150 ms, which can be sufficiently fast tobe used to track the distance between the optical components and thetissue surface and adjust the focal distance accordingly. It may bepossible to produce this type of lens having a response time of about 10ms. Utilizing a variable lens such as the one described above betweenthe collimator and the SECM grating can provide, e.g., a focal distancethat can vary by about ±300 μm or greater.

Various configurations can be provided for the inner housing inaccordance with certain exemplary embodiments of the present invention.For example, a housing formed from transparent material 1700 can beused, as shown in FIG. 17A. Alternatively, a housing can be providedthat includes a transparent window 1710, as shown in FIG. 17B. A housingmay also be provided that includes an opening 1720 between two walls,such as that as shown in FIG. 17C, or an opening adjacent to a motor1730 that may be attached to the housing as shown, e.g., in FIG. 17D.

An exemplary schematic diagram of a control and data recordingarrangement which can be used with the exemplary system shown in FIG. 9is provided in FIG. 18. The arrangement shown in FIG. 18 can beconfigured to record a beam position while acquiring imaging data 1800,which can provide a more precise spatial registration of the imagingdata 1800. As shown in FIG. 18, the imaging data 1800 can be acquired bya data acquisition and control unit 1810. A catheter scanner arrangementmay scan a beam, e.g., using a rotary motor 1820 to provide angularmotion of the beam and a pullback motor 1830 to move the beamlongitudinally. The rotary motor 1820 can be controlled by a rotarymotor controller 1840, and the pullback motor 1830 can be controlled bya pullback motor controller 1850. Each of these control techniques maybe performed using a closed loop operation. The data acquisition andcontrol unit 1810 can direct the motor controller units 1840, 1850 toprovide specified motor velocities and/or positions. Encoder signalsgenerated by the motors 1820, 1830 can be provided to both the motorcontroller units 1840, 1850 and the data acquisition and control unit1810. In this manner, the encoder signals associated with each motor1820, 1830 can be recorded when a line of imaging data 1800 is acquired,thereby allowing a precise beam position to be associated with each lineof data 1800.

Various scanning priorities that may be used in the imaging catheter inaccordance with an exemplary embodiment of the present invention areshown in FIG. 19. For example, an exemplary scanning technique in whichrotational scanning is performed as a first priority and axial(pullback) scanning is performed as a second priority is shown in FIG.19A. This technique can provide a set of data having a helical geometry.In a further scanning technique, the axial scanning can be performed insmall increments, with each axial increment following a full revolution,as shown in FIG. 19B. Alternatively, axial (pullback) scanning can beperformed as a first priority and rotational scanning can be performedas a second priority, which may generate the scanning pattern shown inFIG. 19C. A greater imaging quality can be achieved along a direction ofthe first scan priority. Thus, a choice of scan priority may depend onwhether transverse (rotational) images or axial images are preferred.Imaging of other organs or tissues that may have different symmetriescan be performed in several ways. For example, a circular scanningpattern that may be used to image certain organs is shown in FIG. 19D.

In a further exemplary embodiment of the present invention, a ballooncatheter such as, e.g., the one shown in FIG. 10, can be configured toallow for a rapid-exchange placement procedure using a guidewire. In arapid-exchange placement procedure, a guidewire can first be placed inan organ to be imaged, and the catheter can then be threaded down theguidewire. This procedure can allow easier and more precise placement ofthe catheter in many applications. Various configurations may be used toguide a catheter using a rapid-exchange procedure. For example, FIG. 20Ashows an exemplary guidewire 2000 that passes through a hole 2010 in adistal end of the outer housing 2040. In a second exemplaryconfiguration shown in FIG. 20B, a guidewire 2000 passes through a tube2020 that is attached to the distal end of the outer housing 2040.Alternatively, the guidewire 2000 can be configured to pass through thetube 2020 which may be attached to a proximal end of the outer housing2040, as shown in FIG. 20C.

An exemplary procedure that may be used to position a catheter thatemploys a guidewire in a center lumen of the catheter is illustrated inFIGS. 21A-C. First, the guidewire 2100 can be placed within the organ2150, as shown in FIG. 21A. Next, an outer housing 2110 of the catheter,together with a balloon 2120, can be threaded over the guidewire 2100,as shown in FIG. 21B. Finally, the inner housing 2130, which may containan optical arrangement, can be threaded down the catheter center lumenas shown in FIG. 21C, and an imaging procedure using the opticalarrangement can be performed.

Two exemplary configurations of a balloon catheter are shown in FIG. 22.In FIG. 22A, a device 2200 that may include a source of pressurized airor gas can be used to inflate a balloon 2210. A tube or other smallpassageway 2230 can be provided that is connected to the balloon 2210surrounding the catheter and which allows transfer of the pressurizedair or gas to the balloon 2210. Pressure within the balloon 2210 beinginflated can be monitored using a manometer 2220. This pressure can beused to optimize the balloon inflation as well as to assess placement ofthe catheter by monitoring pressure within a surrounding organ which maybe contacted by the inflated balloon 2210. Alternatively, a passageway2240 can be provided along an outer sheath of the catheter, which canallow transfer of the pressurized air or gas to the balloon 2210, asshown in FIG. 22B. A balloon that is capable of changing its diameter inresponse to pressure changes may be used, where focus depth can becontrolled by varying the balloon diameter and thus moving thesurrounding tissue to be allows transfer of the pressurized air or gasto the balloon 2210. with respect to the imaging lens.

An exemplary catheter design that may be used in accordance with anotherexemplary embodiment of the present invention is shown in FIGS. 23A-23C.This catheter design can be configured to use one or more expandablewire strands 2300 to center an inner optical core of an imaging devicewithin a luminal organ. The catheter may include an additional sheath2310 and a set of expandable wire strands 2300 located within the sheath2310 that may be provided around the outer housing 2320, as shown inFIG. 23A. After placement of the catheter, the wire strands 2300 can bepushed through the sheath 2310 to protrude from the end thereof as shownin FIG. 23B Alternatively, the sheath 2310 can be retracted from theouter housing 2320. A sufficient length of the wire strands 2300 can beexposed around the outer housing 2320 to allow the wire strands 2300 toexpand the surrounding organ or tissue as shown in FIG. 23C, and tocenter the housing 2320. After the imaging procedure is performed, thewire strands 2300 may be pulled back into the sheath 2310 and thecatheter can be removed.

Exemplary OCT and RCM techniques can reject or ignore multiply scatteredlight received from a tissue sample being imaged, and thereby detectsingly backscattered photons that may contain structural information.Each of these techniques, however, can reject multiply scattered lightin a different way.

For example, the RCM techniques may employ confocal selection of lightreflected by tissue being imaged from a tightly focused incident beam.RCM techniques can be implemented by rapidly scanning the focused beamin a plane parallel to the tissue surface, which may provide transverseor en face images of the tissue. A large numerical aperture (NA), whichcan be used with conventional RCM techniques, may yield a very highspatial resolution (e.g., approximately 1-2 μm that can allowvisualization of subcellular structure. Imaging procedures using a highNA, however, can be particularly sensitive to aberrations that can ariseas light propagates through inhomogeneous tissue. Therefore,high-resolution imaging using RCM techniques may be limited to a depthof about 100-400 μm.

The OCT techniques can utilize coherence gating principles for opticalsectioning and may not rely on the use of a high NA lens. OCT techniquesmay thus be performed using an imaging lens having a relatively largeconfocal parameter. This can provide a greater penetration depth intothe tissue being imaged (e.g., approximately 1-3 mm) and across-sectional image format. These advantages may come at the expenseof a reduced transverse resolution, which can be typically on the orderof about 10-30 μm.

Thus, in view of the distinctions described above, the exemplary OCT andRCM techniques can offer different imaging information which may becomplementary. For example, RCM techniques can provide subcellulardetail, whereas OCT techniques can provide, e.g., architecturalmorphology. Imaging information from these two size regimes can becritical for histopathologic diagnosis, and in many cases, it may bedifficult if not impossible to make an accurate diagnosis without usingboth. Although a combination of these disparate imaging techniques mayconventionally utilize extensive engineering efforts which cancompromise performance, SECM and SD-OCT techniques can share certaincomponents. Therefore, a high-performance multi-modality systememploying both of these imaging techniques can be provided that does notinclude a substantial increase in complexity or cost relative to asystem that may use either technique alone.

An overview of an exemplary system that is capable of performing bothSECM techniques and SD-OCT techniques in accordance with an exemplaryembodiment of the present invention is shown in FIG. 24A. In thisexemplary system, a portion of a broadband light source bandwidth can beused for obtaining SECM image data, and a further portion of thebandwidth data can be used, e.g., to obtain SD-OCT data. For example, alight source 2400 can be used to provide electromagnetic energy having abandwidth greater than, e.g., about 100 nm. Devices that may be used asa light source 2400 can include, e.g., a diode-pumped ultrafast laser(such as that available from, e.g., IntegralOCT, Femtolasers ProduktionsGmbH, Vienna, Germany), or an array of super luminescent diodes (whichmay be obtained, e.g., from Superlum, Russia).

A portion of the light source spectrum that may be used for SD-OCT data(e.g., light having a wavelength between about 810-900 nm) can beseparated from a portion of the spectrum that may be used for SECM datausing a wavelength division multiplexer (WDM) 2410 and transmitted to acatheter 2420 and to a reference arm 2445. Light returning from thecatheter 2420 through an SECM optical fiber 2430 and an SD-OCT opticalfiber 2440 can be provided to a spectrometer 2450. The spectrometer 2450may be configured so that approximately half of the elements of theexemplary CCD array 2460 shown in FIG. 24B can detect a signalassociated with the SECM data, and approximately half of the CCDelements can detect a signal associated with the SD-OCT data. The SD-OCTdata can be converted into axial structural data, e.g., by performing aFourier transformation following interpolation of the SD-OCT data fromwavelength space to k-space. For example, if the spectrometer 2450 has aresolution of approximately 0.1 nm, a total SD-OCT ranging depth may begreater than about 2.0 mm. Axial image resolution using the SD-OCTtechnique may be approximately 5 μm.

A schematic overview of an exemplary SECM/SD-OCT probe is shown in FIG.25. This probe is similar to the probe shown, e.g., in FIG. 15, and itfurther includes an arrangement configured to provide an SD-OCT beampath. In order to obtain an SD-OCT beam, an OCT optical fiber 2500 canbe inserted into the inner housing, together with an SECM optical fiber2510. The OCT optical fiber 2500 can be configured to illuminate a smalllens 2520. A confocal parameter and a spot size for the SD-OCT beam canbe selected to achieve cross-sectional imaging over a range of depths.Exemplary values of the confocal parameter spot size can be, e.g., beapproximately 1.1 mm and 25 μm, respectively. The NA of the SD-OCT lens2520 can be selected to be, e.g., approximately 0.02, and a collimatedbeam diameter of the SD-OCT beam can be selected to be, e.g.,approximately 200 μm. A dichroic mirror 2530 can be placed before theSECM grating to reflect the SD-OCT light beam 2540 and transmit the SECMlight beam 2550. The dichroic mirror 2530 shown in FIG. 25 is arrangedat an angle of approximately 45 degrees with respect to the SD-OCT lightbeam 2540. This angle can be increased by using an appropriate coatingon the mirror 2530, which can allow the SD-OCT beam 2540 to overlap theSECM beam 2550 for a more precise spatial registration of the twoimages. Optical aberrations of the SD-OCT beam 2540 which may beproduced, e.g., by a curved window or balloon can be corrected by usinga cylindrical element to pre-compensate for astigmatism as shown in FIG.12B.

A further exemplary embodiment of a catheter probe which may be used forboth SECM imaging and SD-OCT imaging is shown in FIG. 26. Broadbandlight may be provided through a single optical fiber 2600, instead ofthrough two separate fibers 2500, 2510 as shown in FIG. 25. A portion ofthe light which may be used to form an SD-OCT beam 2640 may be reflectedout of the optical path of the SECM beam 2650 using a dichroic mirror2610. The diameter of the SD-OCT beam 2640 may be reduced by an aperture2620 and/or by focusing the SD-OCT beam 2640 using a lens 2630. TheSD-OCT arrangement may also be used to locate a surface of a tissuebeing imaged using an SECM technique, even with SD-OCT depth resolutionsbetween about 20-100 μm. This can be performed even if the bandwidth ofthe SD-OCT beam 2640 is not sufficient to obtain a high quality SD-OCTimage.

Data obtained from an exemplary SD-OCT image can be used to adjust afocal plane of an SECM beam. An exemplary flow diagram illustrating thistechnique is shown in FIG. 27. For example, SD-OCT image data may beobtained from a depth scan (step 2700) and subsequently processed (step2710). The image data may be analyzed and displayed as an SD-OCT image(step 2720). This image data may also be used to determine the locationof a tissue surface (step 2730) using, for example, edge detectionalgorithms. Once the surface location of the tissue has been determined,a variable focus mechanism can be used to adjust a location of a focalplane of the SECM arrangement (step 2740). This focus control techniquecan be performed rapidly (e.g., in less than about 100 ms), which mayallow for real-time tracking and focusing of a tissue surface. Alocation of a tissue edge can be calibrated using an angle that isformed with respect to the SECM beam.

A cross section of an exemplary catheter cable 2800 which may be usedwith certain exemplary embodiments of the present invention is shown inFIG. 28. The cable 2800 may include, e.g., a pullback cable 2810, aplurality of wires 2820 configured to supply electric power to a motor,a focus control cable 2830, a channel 2840 configured to provide a gasor other fluid to an inflatable balloon or membrane, an SECM opticalfiber 2850, and/or an SD-OCT optical fiber 2860.

A schematic illustration of an exemplary SECM probe 2900 is shown inFIG. 29. The probe 2900 includes two prisms 2910 which may be configuredto deflect a beam 2920 before it passes through a grating 2930 and animaging lens 2940. This exemplary configuration can provide more spacewithin the probe 2900 for the objective lens 2940, which can result in ahigher NA and/or a size reduction of the probe 2900.

A further reduction in probe length can be achieved using the exemplaryprobe configuration 3000 shown in FIGS. 30A-30C. The probe 3000 caninclude an inner housing 3010 which may be provided within an outerhousing 3020 while the probe 3000 is delivered to the imaging location,as shown in FIG. 3A. After the probe 3000 is placed and centered withinthe tissue or organ to be imaged, the inner housing 3010 can slidethrough the outer housing 3020 to provide an extended pullback range, asshown in FIGS. 30B and 30C. For example, providing an imaging lens 3020near a center of the inner housing 3010 can provide increased positionalstability at the extreme scanning locations shown in FIGS. 30B and 30C.

An exemplary outer housing 3100 is shown in FIG. 31. The outer housing3100 can be made of rigid materials such as, e.g., stainless steel orplastic. It may include one or more gaps 3110 which can allow light topass therethrough to generate image data without introducing opticalaberrations. Optionally, the gaps 3110 may include transparent windows.

FIG. 32 shows an exemplary probe in accordance with certain exemplaryembodiments of the present invention. The probe 3200 can provide acompact configuration of components and a small overall probe size. Forexample, a cylindrical inner housing 3210 can be configured to rotateand move freely within a cylindrical outer housing 3220, allowing acollimating lens 3230 and an optical fiber 3240 to be placed away from acenter axis of the inner housing 3210. Scanning of a region of tissue tobe imaged can be performed externally, where motion of the inner housing3210 can be controlled using a pullback cable 3250.

In certain exemplary embodiments of the present invention, a liquid suchas, e.g., water or an index-matching oil can be provided in a spacebetween an imaging lens and a surface of the tissue to be imaged.Providing such a liquid can, e.g., improve optical parameters such as aNA and/or reduce back reflections of a light beam used to obtain imagedata.

An exemplary probe configuration 3300 which can provide a high NA forobtaining image data is shown in FIGS. 33A and 33B. For example, aninner housing 3310 can be provided in an outer housing 3320, which mayalso include an uninflated balloon 3330. The uninflated balloon 3330 maybe inflated such that it can expand forward of the outer housing 3320.The inner housing 3310 may then be deployed outside of the outer housing3310 and within the inflated balloon 3340. An elastic arrangement 3350can be provided in a compressed configuration between the inner housing3310 and the outer housing 3320, as shown in FIG. 33A. The elasticarrangement 3350 can be configured to position the inner housing 3310against an inside wall of the inflated balloon 3340 when the innerhousing 3310 is deployed, as shown in FIG. 33B. The inner housing 3310can be configured to scan a region of tissue outside of the inflatedballoon 3340 the balloon area using a pullback cable 3360. The cable3360 can be capable of controlling both rotation and longitudinaltranslation (e.g., pullback) of the inner housing 3310 within theinflated balloon 3340. Spacers 3370 may be used to improve contactbetween the imaging optical arrangement and the wall of the inflatedballoon 3340 or the adjacent tissue surface.

A further exemplary probe configuration 3400 is shown in FIGS. 34A and34B, which can be capable of maintaining an inner probe housing 3410against an inside wall of an outer balloon 3420, in accordance withcertain exemplary embodiments of the present invention. For example, anouter balloon 3420 and an inner balloon 3430, shown uninflated in FIG.34A, can be provided such that they surround the inner housing 3410.Each balloon may be inflated, as shown in FIG. 34B. In this exemplaryconfiguration, the inner housing 3410 may be attached to one face of theinner balloon 3430. Rotational and translational scanning within theouter balloon 3420 may be performed by moving the inner housing 3410together with the inner balloon 3430 relative to the outer balloon 3420.

A still further exemplary probe configuration 3500 is shown in FIGS. 35Aand 35B, which can be capable of maintaining an inner probe housing 3510against an inside wall of an outer balloon 3520, in accordance withcertain exemplary embodiments of the present invention. The outerballoon 3520, shown uninflated in FIG. 35A, may be inflated within anorgan or region of tissue to be imaged. An inner balloon 3530, shownuninflated in FIG. 35A, may be provided between the inner housing 3510and the outer balloon 3520. The inner balloon 3530 may be inflated, asshown in FIG. 35B, and pressure provided by the inner balloon 3530 canbe used to maintain contact between the inner housing 3510 and an innerwall of the outer balloon 3520, as shown in FIG. 35B. The exemplaryprobe configurations 3400 and 3500 shown in FIGS. 34 and 35,respectively, may be used without an outer housing. The uninflatedballoons 3420, 3430, 3520, 3530 may be packed inside an externalenclosure that can be used to deliver the probe 3400, 3500 to a desiredlocation. Such an external enclosure can optionally be formed, e.g.,from a dissolvable material.

An exemplary configuration of an SECM probe 3600 is shown in FIGS.36A-36D, which is capable of providing a spectrally encoded line 3610that lies perpendicular to an axis of an organ or a balloon cylinder. Abottom view of this probe configuration is provided in FIG. 36A, and acorresponding side view is shown in FIG. 36B. FIG. 36C shows a furtherside view in which the probe housing 3640 is deployed within an inflatedballoon 3650, similar to that shown in FIG. 33B. In this exemplaryconfiguration, a longitudinal (e.g., pullback) direction can be aprimary scanning direction, such that the probe housing 3640 is moved inthis longitudinal direction at a relatively fast rate of speed. Scanningin a rotational direction around a longitudinal axis can be performed ata relatively low rate compared to the longitudinal speed. The probe 3600can be provided with positioning arrangements such as those shown, e.g.,in any of FIGS. 33-35. The probe housing 3640 can include a mirror 3620which may be configured to deflect a light beam towards a suitablypositioned grating to provide a spectrally-encoded line 3610 configuredas shown in FIGS. 36A and 36D.

Combination of SD-OCT and SECM imaging arrangements within a probe canprovide a useful apparatus for obtaining structural information ondifferent scales using different image formats. Data obtained for bothimaging techniques can be acquired simultaneously, because theresolutions of the two techniques are different. However, useful scanrates for the two techniques may not be compatible with each other. Forexample, a typical SECM scan rate can be provided using a rotation rate,e.g., of about 1 Hz and a longitudinal pullback speed, e.g., ofapproximately 1 mm/s. Typical scan rates for obtaining SD-OCT image datacan be, e.g., approximately 50-100 Hz in a rotational direction and,e.g., approximately 0.2-0.5 mm/s in a longitudinal direction.

One technique which may be used to obtain comprehensive image data thatis properly sampled for both techniques is to conduct an additionalcomprehensive SD-OCT scan, sampled appropriately, following acquisitionof the SECM data set. This technique may increase the data acquisitiontime for a tissue region by, e.g., approximately 1-2 minutes. Encodersignals obtained for both the rotating and linearly translating motorscan be digitized throughout each scan. The encoder signals can becorrected for shifts in position of a balloon by quantitativelycorrelating SD-OCT images to determine angular and rotational offsetsfor each scan. This technique can provide accurate spatial registrationof the SD-OCT and SECM data sets within about 500 μm.

In a further exemplary embodiment of the present invention, an imagingarrangement provided, e.g., in a probe may be operated in an abbreviatedimaging mode (e.g., ‘scout imaging’) to determine if a catheter whichmay be used to deliver the probe is properly positioned within the organor tissue region to be imaged. A comprehensive set of image data can beobtained after proper catheter placement is confirmed.

In a still further exemplary embodiment of the present invention, aballoon centering catheter may be inflated using a material that isoptically transparent other than air such as, e.g., water, heavy water(D2O), oil, etc. A lubricating agent may also be used to aid insertionof the catheter. In certain exemplary embodiments of the presentinvention, a mucousal removal agent may be applied prior to obtainingimage data to reduce the amount of mucous present in the organ to beimaged, where presence of such mucous may reduce image quality.

The foregoing merely illustrates the principles of the invention.Various modifications and alterations to the described embodiments willbe apparent to those skilled in the art in view of the teachings herein.Indeed, the arrangements, systems and methods according to the exemplaryembodiments of the present invention can be used with any OCT system,OFDI system, SD-OCT system or other imaging systems, and for examplewith those described in International Patent ApplicationPCT/US2004/029148, filed Sep. 8, 2004, U.S. patent application Ser. No.11/266,779, filed Nov. 2, 2005, and U.S. patent application Ser. No.10/501,276, filed Jul. 9, 2004, the disclosures of which areincorporated by reference herein in their entireties. It will thus beappreciated that those skilled in the art will be able to devisenumerous systems, arrangements and methods which, although notexplicitly shown or described herein, embody the principles of theinvention and are thus within the spirit and scope of the presentinvention. In addition, to the extent that the prior art knowledge hasnot been explicitly incorporated by reference herein above, it isexplicitly being incorporated herein in its entirety. All publicationsreferenced herein above are incorporated herein by reference in theirentireties.

1. An apparatus comprising: at least one first arrangement configured toforward an electromagnetic radiation to an anatomical structure, andcontinuously scan an entire region of at least one portion of theanatomical structure using the electromagnetic radiation to generate atleast one signal, wherein the entire region has an area that is greaterthan 1 mm2; and at least one second arrangement configured to receivethe particular signal and to generate at least one image based on thesignal that has a transverse resolution that is below 10 μm.
 2. Theapparatus according to claim 1, wherein the entire region is a volume ofthe structure.
 3. The apparatus according to claim 1, wherein the atleast one image is contiguous without substantial gaps therein.
 4. Theapparatus according to claim 1, wherein the at least one portion isprovided on a surface of the anatomical structure.
 5. The apparatusaccording to claim 1, wherein the at least one portion is provided belowa surface of the anatomical structure.
 6. The apparatus according toclaim 1, wherein the electromagnetic radiation comprises a plurality ofwavelengths.
 7. The apparatus according to claim 1, wherein theelectromagnetic radiation comprises one or more wavelengths that varyover time.
 8. The apparatus according to claim 1, wherein at least oneof the at least one first arrangement or the at least one secondarrangement includes a microscope arrangement, and where the microscopearrangement is at least one of a multiphoton microscope arrangement or aconfocal microscope arrangement.
 9. The apparatus according to claim 8,wherein the microscope arrangement includes a spectral encodingarrangement.
 10. The apparatus according to claim 1, wherein the atleast one anatomical structure is an internal organ.
 11. The apparatusaccording to claim 1, wherein at least one of the at least one firstarrangement forwards the electromagnetic radiation via an optical fiberarrangement, or at least one second arrangement receives the signal viaan optical fiber arrangement.
 12. The apparatus according to claim 11,wherein the optical fiber arrangement includes a plurality ofelectromagnetic radiation guiding arrangements.
 13. The apparatusaccording to claim 1, wherein the signal is associated with at least oneportion of an intensity of the electromagnetic radiation received fromthe anatomical structure.
 14. The apparatus according to claim 1,wherein the at least one first arrangement is provided in a probe. 15.The apparatus according to claim 1, wherein the first arrangementincludes at least one optical component which is configured tocompensate for at least one optical aberration.
 16. The apparatusaccording to claim 15, wherein the at least one optical componentcomprises a curved surface.
 17. The apparatus according to claim 16,wherein the at least one optical aberration is an astigmatism.
 18. Theapparatus of claim 1, further comprising a positioning arrangementconfigured to position at least one of the at least one firstarrangement or the at least one second arrangement at a particularlocation relative to the anatomical structure.
 19. The apparatusaccording to claim 1, wherein the at least one first arrangement isfurther configured to position a focus of the electromagnetic radiationat a plurality of depths within the anatomical structure.
 20. Theapparatus according to claim 1, further comprising at least one thirdarrangement configured to: generate a further signal; determine at leastone location of a particular section associated with the anatomicalstructure based on the further signal; and control at least one of amotion or a position of a focus of the at least one electromagneticradiation to a further location within the anatomical structure based onthe further signal.
 21. The apparatus according to claim 20, wherein thefurther signal is the signal.
 22. The apparatus according to claim 21,wherein the further signal is at least one of an interferometric signal,a time-of-flight signal, or an intensity of the electromagneticradiation.
 23. The apparatus according to claim 20, wherein the furthersignal is associated with at least one distance between at least onelocation within the region of the anatomical structure and at least onecomponent of the at least one first arrangement. 24-40. (canceled)
 41. Amethod for imaging a region of an anatomical structure, comprising:forwarding at least one electromagnetic radiation to an anatomicalstructure; continuously scanning an entire region of at least oneportion of the anatomical structure using the electromagnetic radiation,wherein the entire region has an area that is greater than 1 mm2;obtaining at least one signal based on the electromagnetic radiation;and generating at least one image based on the signal, wherein the imagehas a transverse resolution that is below 10 μm. 42-43. (canceled) 44.The apparatus according to claim 1, further comprising: at least onethird arrangement which is different from the first and secondarrangements and configured to receive the signal and an additionalsignal from a reference to generate an interferometric signal.
 45. Theapparatus according to claim 1, further comprising at least one thirdarrangement configured to automatically control a position of a focus ofthe at least one first arrangement as a function of the signal to apredetermined location within the anatomical structure.
 46. Theapparatus according to claim 45, wherein the automatic control of theposition of the focus by the at least one third arrangement is performedapproximately parallel to an optical axis of the electromagneticradiation that impinges on the anatomical structure.
 47. The apparatusaccording to claim 45, wherein the predetermined location is determinedbased on an interferometric signal.
 48. The apparatus according to claim1, wherein the signal is at least one signal provided from theanatomical structure.